diff --git a/RefactoringEssentials.2017/RefactoringEssentials.csproj b/RefactoringEssentials.2017/RefactoringEssentials.csproj
index a56c0ba2..020c1fbb 100644
--- a/RefactoringEssentials.2017/RefactoringEssentials.csproj
+++ b/RefactoringEssentials.2017/RefactoringEssentials.csproj
@@ -169,6 +169,9 @@
     <Compile Include="..\RefactoringEssentials\CSharp\CodeRefactorings\Synced\ContractEnsuresNotNullReturnRefactoringProvider.cs">
       <Link>CSharp\CodeRefactorings\Synced\ContractEnsuresNotNullReturnRefactoringProvider.cs</Link>
     </Compile>
+    <Compile Include="..\RefactoringEssentials\CSharp\CodeRefactorings\Synced\ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider.cs">
+      <Link>CSharp\CodeRefactorings\Synced\ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider.cs</Link>
+    </Compile>
     <Compile Include="..\RefactoringEssentials\CSharp\CodeRefactorings\Synced\ContractRequiresNotNullCodeRefactoringProvider.cs">
       <Link>CSharp\CodeRefactorings\Synced\ContractRequiresNotNullCodeRefactoringProvider.cs</Link>
     </Compile>
diff --git a/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractEnsuresNotNullReturnRefactoringProvider.cs b/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractEnsuresNotNullReturnRefactoringProvider.cs
index e5e251c5..58318ae7 100644
--- a/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractEnsuresNotNullReturnRefactoringProvider.cs
+++ b/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractEnsuresNotNullReturnRefactoringProvider.cs
@@ -51,7 +51,7 @@ protected IEnumerable<CodeAction> GetActions(Document document, SyntaxNode root,
 
         protected IEnumerable<CodeAction> GetActions(Document document, SyntaxNode root, AccessorDeclarationSyntax node)
         {
-            var propertyOrIndexerDeclaration = node.Ancestors().Where(n => n.GetType().Equals(typeof(PropertyDeclarationSyntax)) || n.GetType().Equals(typeof(IndexerDeclarationSyntax))).FirstOrDefault();
+            var propertyOrIndexerDeclaration = node.Ancestors().FirstOrDefault(n => n.GetType().Equals(typeof(PropertyDeclarationSyntax)) || n.GetType().Equals(typeof(IndexerDeclarationSyntax)));
 
             var nullableType = propertyOrIndexerDeclaration.ChildNodes().OfType<NullableTypeSyntax>().FirstOrDefault();
             
diff --git a/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider.cs b/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider.cs
new file mode 100644
index 00000000..68209283
--- /dev/null
+++ b/RefactoringEssentials/CSharp/CodeRefactorings/Synced/ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider.cs
@@ -0,0 +1,93 @@
+using System.Linq;
+using System.Threading;
+using System.Collections.Generic;
+using Microsoft.CodeAnalysis.CodeRefactorings;
+using Microsoft.CodeAnalysis;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.Simplification;
+using Microsoft.CodeAnalysis.Formatting;
+
+namespace RefactoringEssentials.CSharp.CodeRefactorings
+{
+    [ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = "Add a Contract to specify the string parameter must not be null or empty")]
+    /// <summary>
+    /// Creates a 'Contract.Requires(param != null);' contract for a parameter.
+    /// </summary>
+    public class ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider : CodeContractsCodeRefactoringProvider
+    {
+        #region ICodeActionProvider implementation
+        public override async Task ComputeRefactoringsAsync(CodeRefactoringContext context)
+        {
+            var codeContractsContext = await CodeContractsContext(context);
+            if (codeContractsContext == null)
+                return;
+
+            var foundNode = (ParameterSyntax)codeContractsContext.Node.AncestorsAndSelf().FirstOrDefault(n => n is ParameterSyntax);
+            if (foundNode == null)
+                return;
+
+            foreach (var action in GetActions(codeContractsContext.Document, codeContractsContext.SemanticModel, codeContractsContext.Root, codeContractsContext.TextSpan, foundNode))
+                context.RegisterRefactoring(action);
+        }
+        #endregion
+
+        protected IEnumerable<CodeAction> GetActions(Document document, SemanticModel semanticModel, SyntaxNode root, TextSpan span, ParameterSyntax node)
+        {
+            if (!node.Identifier.Span.Contains(span))
+                yield break;
+
+            var parameter = node;
+            var bodyStatement = parameter.Parent.Parent.ChildNodes().OfType<BlockSyntax>().FirstOrDefault();
+            if (bodyStatement == null)
+                yield break;
+
+            var parameterSymbol = semanticModel.GetDeclaredSymbol(node);
+            var type = parameterSymbol.Type;
+            if (type.SpecialType != SpecialType.System_String || HasReturnContract(bodyStatement, parameterSymbol.Name))
+                yield break;
+
+            yield return CreateAction(
+                node.Identifier.Span
+                , t2 => {
+                    var newBody = bodyStatement.WithStatements(SyntaxFactory.List<StatementSyntax>(new[] { CreateContractRequiresCall(node.Identifier.ToString()) }.Concat(bodyStatement.Statements)));
+
+                    var newRoot = (CompilationUnitSyntax)root.ReplaceNode((SyntaxNode)bodyStatement, newBody);
+
+                    if (UsingStatementNotPresent(newRoot)) newRoot = AddUsingStatement(node, newRoot);
+
+                    return Task.FromResult(document.WithSyntaxRoot(newRoot));
+                }
+                , "Add contract requiring parameter must not be null or empty"
+            );
+        }
+
+        static StatementSyntax CreateContractRequiresCall(string parameterName)
+        {
+            return SyntaxFactory.ParseStatement($"Contract.Requires(string.IsNullOrEmpty({parameterName}) == false);\r\n").WithAdditionalAnnotations(Formatter.Annotation, Simplifier.Annotation);
+        }
+
+        static bool HasReturnContract(BlockSyntax bodyStatement, string parameterName)
+        {
+            var workspace = new AdhocWorkspace();
+
+            foreach (var expression in bodyStatement.DescendantNodes().OfType<ExpressionStatementSyntax>())
+            {
+                var formatted = Formatter.Format(expression, workspace).ToString();
+
+                if (formatted == $"Contract.Requires(string.IsNullOrEmpty({parameterName}) == false);")
+                    return true;
+
+                if (formatted == $"Contract.Requires(false == string.IsNullOrEmpty({parameterName}));")
+                    return true;
+
+                if (formatted == $"Contract.Requires(!string.IsNullOrEmpty({parameterName}));")
+                    return true;
+            }
+            return false;
+        }
+    }
+}
diff --git a/RefactoringEssentials/CodeAnalyzers.CSharp.html b/RefactoringEssentials/CodeAnalyzers.CSharp.html
index 2cba20b8..1fdf8bef 100644
--- a/RefactoringEssentials/CodeAnalyzers.CSharp.html
+++ b/RefactoringEssentials/CodeAnalyzers.CSharp.html
@@ -15,7 +15,7 @@
 
     -->
     <h2>Supported Code Analyzers</h2>
-    <p>119 code analyzers for C#</p>
+    <p>120 code analyzers for C#</p>
     <ul>
       <li>Suggests using the class declaring a static function when calling it (AccessToStaticMemberViaDerivedTypeAnalyzer)</li>
       <li>When initializing explicitly typed local variable or array type, array creation expression can be replaced with array initializer. (ArrayCreationCanBeReplacedWithArrayInitializerAnalyzer)</li>
@@ -131,6 +131,7 @@ <h2>Supported Code Analyzers</h2>
       <li>Warns when a culture-aware 'IndexOf' call is used by default. (StringIndexOfIsCultureSpecificAnalyzer)</li>
       <li>Warns when a culture-aware 'LastIndexOf' call is used by default. (StringLastIndexOfIsCultureSpecificAnalyzer)</li>
       <li>Warns when a culture-aware 'StartsWith' call is used by default. (StringStartsWithIsCultureSpecificAnalyzer)</li>
+      <li>Use 'var' keyword when possible (SuggestUseVarKeywordEvidentAnalyzer)</li>
       <li>[ThreadStatic] doesn't work with instance fields (ThreadStaticAtInstanceFieldAnalyzer)</li>
       <li>Parameter is never used (UnusedParameterAnalyzer)</li>
       <li>Type parameter is never used (UnusedTypeParameterAnalyzer)</li>
diff --git a/RefactoringEssentials/CodeRefactorings.CSharp.html b/RefactoringEssentials/CodeRefactorings.CSharp.html
index 7480f7ee..085072c3 100644
--- a/RefactoringEssentials/CodeRefactorings.CSharp.html
+++ b/RefactoringEssentials/CodeRefactorings.CSharp.html
@@ -15,7 +15,7 @@
 
     -->
     <h2>Supported Refactorings</h2>
-    <p>101 code refactorings for C#</p>
+    <p>104 code refactorings for C#</p>
     <ul>
       <li>Adds another accessor (AddAnotherAccessorCodeRefactoringProvider)</li>
       <li>Add braces (AddBracesCodeRefactoringProvider)</li>
@@ -34,6 +34,7 @@ <h2>Supported Refactorings</h2>
       <li>Compute constant value (ComputeConstantValueCodeRefactoringProvider)</li>
       <li>Add a Contract to specify the return value must not be null (ContractEnsuresNotNullReturnCodeRefactoringProvider)</li>
       <li>Add a Contract to specify the parameter must not be null (ContractRequiresNotNullCodeRefactoringProvider)</li>
+      <li>Add a Contract to specify the string parameter must not be null or empty (ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider)</li>
       <li>Convert anonymous method to lambda expression (ConvertAnonymousMethodToLambdaCodeRefactoringProvider)</li>
       <li>Convert auto-property to computed propertyy (ConvertAutoPropertyToPropertyCodeRefactoringProvider)</li>
       <li>Replace bitwise flag comparison with call to 'Enum.HasFlag' (ConvertBitwiseFlagComparisonToHasFlagsCodeRefactoringProvider)</li>
@@ -102,10 +103,12 @@ <h2>Supported Refactorings</h2>
       <li>Replace assignment with postfix expression (ReplaceAssignmentWithPostfixExpressionCodeRefactoringProvider)</li>
       <li>Replace auto-property with property that uses a backing field (ReplaceAutoPropertyWithPropertyAndBackingFieldCodeRefactoringProvider)</li>
       <li>Convert cast to 'as'. (ReplaceDirectCastWithSafeCastCodeRefactoringProvider)</li>
+      <li>Replace type with 'var' (ReplaceExplicitTypeWithVarCodeRefactoringProvider)</li>
       <li>Replace operator assignment with assignment (ReplaceOperatorAssignmentWithAssignmentCodeRefactoringProvider)</li>
       <li>Replace postfix expression with assignment (ReplacePostfixExpressionWithAssignmentCodeRefactoringProvider)</li>
       <li>Replace property that uses a backing field with auto-property (ReplacePropertyWithBackingFieldWithAutoPropertyCodeRefactoringProvider)</li>
       <li>Convert 'as' to cast. (ReplaceSafeCastWithDirectCastCodeRefactoringProvider)</li>
+      <li>Replaces 'var' with explicit type specification (ReplaceVarWithExplicitTypeCodeRefactoringProvider)</li>
       <li>Replace assignment with operator assignment (ReplaceWithOperatorAssignmentCodeRefactoringProvider)</li>
       <li>Reverse the direction of a for  (ReverseDirectionForForLoopCodeRefactoringProvider)</li>
       <li>Split declaration list (SplitDeclarationListCodeRefactoringProvider)</li>
diff --git a/RefactoringEssentials/RefactoringEssentials.csproj b/RefactoringEssentials/RefactoringEssentials.csproj
index 2203b1c4..919a3118 100644
--- a/RefactoringEssentials/RefactoringEssentials.csproj
+++ b/RefactoringEssentials/RefactoringEssentials.csproj
@@ -58,6 +58,7 @@
     <Compile Include="Converter\CodeWithOptions.cs" />
     <Compile Include="Converter\ConversionResult.cs" />
     <Compile Include="CSharp\CodeRefactorings\Custom\AddNullCheckCodeRefactoringProvider.cs" />
+    <Compile Include="CSharp\CodeRefactorings\Synced\ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider.cs" />
     <Compile Include="CSharp\CodeRefactorings\Synced\ContractRequiresNotNullCodeRefactoringProvider.cs" />
     <Compile Include="CSharp\CodeRefactorings\Synced\ContractEnsuresNotNullReturnRefactoringProvider.cs" />
     <Compile Include="CSharp\CodeRefactorings\Synced\MergeNestedIfAction.cs" />
diff --git a/Tests.2017/Tests.csproj b/Tests.2017/Tests.csproj
index 4d3368af..7209b6c2 100644
--- a/Tests.2017/Tests.csproj
+++ b/Tests.2017/Tests.csproj
@@ -287,7 +287,10 @@
     <Compile Include="..\Tests\CSharp\CodeRefactorings\ContractEnsuresNotNullReturnTests.cs">
       <Link>CSharp\CodeRefactorings\ContractEnsuresNotNullReturnTests.cs</Link>
     </Compile>
-    <Compile Include="..\Tests\CSharp\CodeRefactorings\ContractRequiresNotNullTests.cs">
+    <Compile Include="..\Tests\CSharp\CodeRefactorings\ContractRequiresStringNotNullOrEmptyTests.cs">
+      <Link>CSharp\CodeRefactorings\ContractRequiresNotNullTests.cs</Link>
+    </Compile>
+    <Compile Include="..\Tests\CSharp\CodeRefactorings\ContractRequiresStringNotNullOrEmptyTests.cs">
       <Link>CSharp\CodeRefactorings\ContractRequiresNotNullTests.cs</Link>
     </Compile>
     <Compile Include="..\Tests\CSharp\CodeRefactorings\ConvertAnonymousMethodToLambdaTests.cs">
diff --git a/Tests/CSharp/CodeRefactorings/ContractRequiresStringNotNullOrEmptyTests.cs b/Tests/CSharp/CodeRefactorings/ContractRequiresStringNotNullOrEmptyTests.cs
new file mode 100644
index 00000000..79657762
--- /dev/null
+++ b/Tests/CSharp/CodeRefactorings/ContractRequiresStringNotNullOrEmptyTests.cs
@@ -0,0 +1,186 @@
+using System;
+using NUnit.Framework;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis;
+using System.Collections.Immutable;
+using RefactoringEssentials.CSharp.CodeRefactorings;
+
+namespace RefactoringEssentials.Tests.CSharp.CodeRefactorings
+{
+    [TestFixture]
+    public class ContractRequiresStringNotNullOrEmptyTests : CSharpCodeRefactoringTestBase
+    {
+        [Test]
+        public void TestLambda()
+        {
+            Test<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test ()
+    {
+        var lambda = (string $s, int e) => {
+        };
+    }
+}", @"using System.Diagnostics.Contracts;
+
+class Foo
+{
+    void Test ()
+    {
+        var lambda = (string s, int e) => {
+            Contract.Requires(string.IsNullOrEmpty(s) == false);
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestAnonymousMethod()
+        {
+            Test<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test ()
+    {
+        var lambda = delegate(string $-[s]-, object e) {
+        };
+    }
+}", @"using System.Diagnostics.Contracts;
+
+class Foo
+{
+    void Test ()
+    {
+        var lambda = delegate(string s, object e) {
+            Contract.Requires(string.IsNullOrEmpty(s) == false);
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestContractAlreadyPresentEqualsFalseFormat()
+        {
+            TestWrongContext<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test ()
+    {
+        var lambda = (string $s, int e) => {
+            Contract.Requires(string.IsNullOrEmpty(s) == false);
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestContractAlreadyPresentFalseEqualsFormat()
+        {
+            TestWrongContext<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test ()
+    {
+        var lambda = (string $s, int e) => {
+            Contract.Requires(false==string.IsNullOrEmpty(s));
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestContractAlreadyPresentNegateFormat()
+        {
+            TestWrongContext<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test ()
+    {
+        var lambda = (string $s, int e) => {
+            Contract.Requires(!string.IsNullOrEmpty(s));
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestDifferentContractAlreadyPresent()
+        {
+            Test<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test ()
+    {
+        var lambda = (string $s, int e) => {
+            Contract.Requires(string.IsNullOrEmpty(notS) == false);
+        };
+    }
+}", @"using System.Diagnostics.Contracts;
+
+class Foo
+{
+    void Test ()
+    {
+        var lambda = (string s, int e) => {
+            Contract.Requires(string.IsNullOrEmpty(s) == false);
+            Contract.Requires(string.IsNullOrEmpty(notS) == false);
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestUsingStatementAlreadyPresent()
+        {
+            Test<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"using System.Diagnostics.Contracts;
+class Foo
+{
+    void Test ()
+    {
+        var lambda = (string $s, int e) => {
+        };
+    }
+}", @"using System.Diagnostics.Contracts;
+class Foo
+{
+    void Test ()
+    {
+        var lambda = (string s, int e) => {
+            Contract.Requires(string.IsNullOrEmpty(s) == false);
+        };
+    }
+}");
+        }
+
+        [Test]
+        public void TestPopupOnlyOnName()
+        {
+            TestWrongContext<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+	void Test ($string param)
+	{
+	}
+}");
+        }
+
+        [Test]
+        public void Test_OldCSharp()
+        {
+            var parseOptions = new CSharpParseOptions(
+                LanguageVersion.CSharp5,
+                DocumentationMode.Diagnose | DocumentationMode.Parse,
+                SourceCodeKind.Regular,
+                ImmutableArray.Create("DEBUG", "TEST")
+            );
+
+            Test<ContractRequiresStringNotNullOrEmptyCodeRefactoringProvider>(@"class Foo
+{
+    void Test (string $test)
+    {
+    }
+}", @"using System.Diagnostics.Contracts;
+
+class Foo
+{
+    void Test (string test)
+    {
+        Contract.Requires(string.IsNullOrEmpty(test) == false);
+    }
+}", parseOptions: parseOptions);
+        }
+    }
+}
diff --git a/Tests/Tests.csproj b/Tests/Tests.csproj
index 64c27dcb..56bb8497 100644
--- a/Tests/Tests.csproj
+++ b/Tests/Tests.csproj
@@ -135,6 +135,7 @@
     <Compile Include="CSharp\CodeFixes\InvalidConversionTests.cs" />
     <Compile Include="CSharp\CodeFixes\ReturnMustNotBeFollowedByAnyExpressionCodeFixProviderTests.cs" />
     <Compile Include="CSharp\CodeFixes\UnreachableCodeTests.cs" />
+    <Compile Include="CSharp\CodeRefactorings\ContractRequiresStringNotNullOrEmptyTests.cs" />
     <Compile Include="CSharp\CodeRefactorings\ContractRequiresNotNullTests.cs" />
     <Compile Include="CSharp\CodeRefactorings\ContractEnsuresNotNullReturnTests.cs" />
     <Compile Include="CSharp\CodeRefactorings\GenerateSwitchLabelsTests.cs" />